a nobleman of the highest rank 公爵 the Duke of Edinburgh 爱丁堡公爵
(in some parts of Europe, especially in the past) a male leader of a small independent state （尤指旧时欧洲部分地区小公国的）君主 see also archduke, duchess, duchy, grand duke
Word OriginOld English (denoting the ruler of a duchy), from Old French duc, from Latin dux, duc- ‘leader’; related to ducere ‘to lead’.